The Milwaukee Journal Sentinel reports the DNR and U.S. Geological Survey decided to withdraw their application to use the bacteria on Keyes Lake in Florence County after the state agriculture department received about 15 letters opposing the experiment, including letters from county officials who expressed safety concerns.

The agencies had wanted to use a bacteria known by the trade name Zequanox, which they said would kill invasive zebra mussels but not native mussels.

Zebra mussels have been found in 163 lakes and rivers since they turned up in inland Wisconsin lakes in 1994.